At the top of this forum is a 'Sticky' thread, titled Cleaning up Text Pasted from Websites, E-mails, PDFs etc., for cleaning up documents such as you describe: https://www.msofficeforums.com/word/...s-e-mails.html

In all likelihood the delays you're experiencing are due to Word having to repaginate the document every time you delete a paragraph break. Switching to Draft view and switching off background repagination may help.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]